Evolution of tune styles

Most of our traditional dance tunes are anonymous - whenever tunes are labelled "trad" this means that a, they are recognised as part of our aural tradition; b, no one has claimed them as their own, c, they are free to use, part of our shared tradition. However someone must have written them at some point and somewhere. What are the inspirations for these tunes, and why is there such a strong sense that a tune is "English" or "Irish"?

An idea that I've come across is that tunes reflect the landscape and the language / accent of the local population. While I like this idea a lot, I think only a little but likely that tunes do reflect the pace and common rhythms in our spoken language. Perhaps in some distant way tunes might reflect the way we experience the landscape, but it has to come back to the human experience.

I think that performance practise has a lot to do with where tunes feel like they come from. It's very possible to take an Irish jig, play it half to 2/3rds speed with a bit more swing and make it feel like a morris tune. If there are different dances used in each country then different ways of playing the tune will evolve with them.

I think the biggest factor is that isolated musics will evolve in their own direction and tiny intial differences will grow to much bigger ones. Musical performance practises are iterative - I hear what you do and make a tiny adjustment, so does the fiddler next door, so does the flute player etc...etc... We play together and come back towards a more unified style and then the tiny incremental changes start again, layers upon layers of revisiting blowing tiny changes into huge ones. Physicists would say: sensitive dependancy on initial conditions.

Maybe there really wasn't much of a difference between the styles initially but over years different sounds have evolved? You can certainly find early tunes, often slip jigs or single jigs, that are present in both English and Irish traditions and are old tunes in both. The next question that presents itself is what in our social history fostered the development of tunes in each area and why did those players not meet?

Also, now as more and more traditional players travel to learn from each other and hear recordings from all over, is our style becoming more unified?